The present invention relates to a photo-electric energy transducing semiconductor device which exhibits improved operating characteristics.
In the process of growing an oxide on a P type doped silicon, the interfacial portion between the oxide and the silicon semiconductor shows the P to N conductivity inversion behavior and thus results in an extremely shallow PN junction barrier between the oxide layer and the silicon semiconductor. This is due to the well known fact that unsaturated combination occurs at the interfacial portion by virtue of shortage of oxygen, and thereby positive charges are provided and stabilized thereon which has the property of inducing negative charges at the interfacial portion near the silicon semiconductor. The result is the formation of a PN junction barrier of the depth of about 10A. Application of the thus obtained PN junction device to photo diodes gives some advantages, i.e., remarkable enhancement in sensitivity in visible light and ultraviolet light regions in particular.
While several prior art photodiodes employing the negative charge induced channel have been proposed, satisfactory operating characteristics have not been obtained; dark current is large and series resistance is large and the linear characteristic of short current against illumination intensity is poor.